This proposal is submitted in response to RFA-AI-09-027, Partnerships for Biodefense Food- and Water-borne Diseases (RO1). Our proposal targets the development of immunotherapy against hemolytic uremic syndrome (HUS) caused by Shiga toxin (Stx)-producing E. coli (STEC). STEC strains are serious Category B pathogens associated primarily with food- and water-borne acquired disease, and represent an important global emerging infection with relevance to food- borne illness and potential bioterrorism. The virulence of STEC is underscored by the very low infectious dose required to produce clinical disease. The treatment of STEC infection is complicated by potentially adverse consequences of routine administration of antibiotics. Diarrhea- associated HUS (D+HUS) is a life-threatening complication of STEC infection, primarily the O157:H7 serotype, in children and the elderly that is heralded by the sudden onset of pallor and oliguria. It is associated with significant morbidity and, despite improvements in pediatric intensive care, the mortality rate from this disease remains 3-5%. There is no proven therapy for HUS. Our team has developed and characterized a panel of neutralizing human monoclonal antibodies (HuMAb) which are highly active in vitro and in vivo against Stx2 or Stx1. These antibodies have undergone extensive evaluation in animal models in our laboratory. Funding (3.5 years) is requested to support cGMP manufacture and pre-clinical studies of the most efficacious HuMAb, 5C12, in addition to the submission of an IND application for Phase I and II clinical trials. Specific Aim 1. Cell line development and production of the research cell bank. Specific Aim 2. Manufacturing process optimization and non-GMP lot production. Specific Aim 3. Preclinical evaluation of the non-GMP HuMAb 5C12. Specific Aim 4. Production of cGMP HuMAb 5C12 for use in Phase I and II clinical trials. Specific Aim 5. Preparation and submission of an Investigational New Drug (IND) application. The significance of this proposal is to facilitate the development of a safe and effective immunotherapeutic biological product that can be given to individuals exposed to an accidental or deliberate (bioterrorism) STEC contamination of food or water sources.